There are two groups: Those who disbelieved in Islam and opposed the messenger of Allah (saws), and those who had believed and were being persecuted and still stood up in the face the leaders of Quraisy during that time. Allah (swt) explains that all the battles between truth and falsehood which happened are trials.

(… وَكَذَٰلِكَ فَتَنَّا بَعْضَهُم بِبَعْضٍ ) (And thus We have tried some of them through others …): Meaning, the group who believed and the group who had not believed.

(… لِّيَقُولُوا أَهَٰؤُلَاءِ مَنَّ اللَّهُ عَلَيْهِم مِّن بَيْنِنَا… ) (…that the disbelievers might say, “Is it these whom Allah has favored among us?”…): They deem weak the poor and needy who have believed in the Prophet (saws), and say: “Has Allah favoured these (poor believers) among all of us?” So, Allah (swt) answers:

(  أَلَيْسَ اللَّهُ بِأَعْلَمَ بِالشَّاكِرِينَ… ) (…Is not Allah most knowing of those who are grateful?): So, Allah (swt) knows the ones who are grateful. They are those who are patient during times of trial, and grateful in times of blessing. The grateful person is the true believer whom, if afflicted with a misfortune, says: Inna lillah wa inna ilaihi raji’un (Verily, we belong to Allah, and verily, to Him we return), and then leaves the issue to Allah (swt).